Cytochrome o terminal oxidase complex is the component of the aerobic respiratory chain which reacts with oxygen, reducing it to water with the concomitant transport of 4 protons across the membrane. Also known as the cytochrome bo complex, cytochrome o ubiquinol oxidase contains four subunits, two heme b cofactors and a copper atom which is believed to be the oxygen active site. This complex is structurally related to the cytochrome caa3 oxidases which utilize cytochrome c as the reductant and contain heme a cofactors, as well as the intermediate form aa3 oxidases which also react directly with quinones as the reductant. [Energy metabolism, Electron transport]
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